Method of coating fibers using shear thinning gel forming materials



Oct. 13, 1970 R. WONG ETAL A 3,533,768 METHOD OF COATING FIBERS USING SHEAR THINNING' GEL FORMING MATERIALS Filed Sept. 25, 19,68

RATE OF sHEAR RATE OF SHEAR RATE OF sHEAR sHEAR STRESS SHEAR STRESS vsHEAR sTREss,

Eig-i Eigi Fig-i RATE OF SHEAR RATE OF SHEAR RATE OF SHEAR SHEAR STRESS SHEAR STRESS SHEAR sTREss Big-A Eigi llig-li ROBE/P7 WOA/G & HOME/R 6. H/AL INVENTORS A TTORN E YS United States Patent 3,533,768 METHOD OF COATIYG FIBERS USING SHEAR THINNING GEL FORMING MATERIALS Robert Wong, Granville, and Homer G. Hill, Newark,

Ohio, assignors to Owens-Corning Fiberglas Corporation, a corporation of Delaware Continuation-impart of application Ser. No. 573,870, Aug. 22, 1966. This application Sept. 25, 1968, Ser. No. 762,435

Int. Cl. C03c /02 US. Cl. 65-3 26 Claims ABSTRACT OF THE DISCLOSURE An improved method of coating fibers and particularly glass fibers with a solution of materials containing a reversible shear thinning gel producing agent which causes the coating to be transformed into a shear thinning gel under predetermined conditions. The uncoated fibers, however, are preferably drawn through the gel to subject the reversible shear thinning gel to shear which causes the materials to flow around and adhere to the fibers, following which the coating reverts to a gel.

CROSS REFERENCES TO RELATED APPLICATIONS The present application is a continuation-in-part application of our copending application Ser. No. 573,870 filed Aug. 22, 1966, and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a new and improved method for coating fibers, and particularly glass fibers at forming; and to the fibers coated thereby.

The technology which has been developed for the production of glass fibers, presently makes possible the production of fibers having a diameter of from approximately 0.0001 inch to aproximately 0.0004 inch, at a rate of from approximately 10,000 feet per minute to approximately 15,000 feet per minute. Glass fibers are produced from small streams of molten glass which exude through tiny orifices located in what is called a bushing. Conventionally, bushings have 204 such orifices. The tiny streams of molten glass which issue from the bushing are attenuated by pulling the fibers until the diameters given above result, and during which time the streams cool and rigidify into what are called filaments. These filaments are then coated with a protective film for the purpose of preventing glass to glass abrasion, and following which they are brought together to form a strand. This strand is coiled upon a spool to form a package. During formation of the package, the strand is traversed back and forth across the spool by a device which is called a traverse, and which is located between the point where the coating materials are applied, and the rotating spool on which the package is made. The spool is rotated by what is called a winding drum, and the pulling action supplied by the winding drum attenuates the molten streams of glass, pulls the filaments past the coating applicator, and through the traverse, and coils the strand onto the package. The winding drum is usually located approximately 10 feet from the bushing, so that the entire forming operation is carried out in a fraction of a second.

The problem of abrasion of glass upon glass is a serious one and has generally been a controlling factor in the rate at which this technology has developed. The seriousness of the problem has caused the wide spread theory that glass to glass abrasion can only be prevented by a solid film of material between the filaments to at all times assure physical separation of the filaments. Regardless "ice of the validity of this theory its acceptance by the art has not caused the art to develop a coating which is completely satisfactory under all conditions for use in separating the filaments during forming. Where the strands are to be woven into textiles, it will be apparent that theamount of film forming materials which can be used must be held within certain percentages of the total weight of the strand in order that the strand will not be unduly stiff. Dyes will not color the glass itself, and so the coatings which are used must either be capable of being dyed, or must be capable of being removed and later replaced by a material capable of being dyed. Where the lass is to be used for reinforcing plastic materials, the bond between the coatings and the glass filaments is very important, as Well as the compatibility of the coating with the later applied resin Which the coated strand is intended to reinforce.

The technology in its forty some years of existence has examined all types of materials for their suitability as coatings on glass fibers in an attempt to find one which is universal in that fibers coated therewith can be used for all known subsequent uses of coated glass strand. The art has tried all kinds of resins, either as emulsions, or as solutions in organic solvents, but all lack some desired characteristics, and usually suffer from high tensions during weaving operations. In addition, organic solvents create explosion hazards. Explosion hazards require expensive equipment to overcome. In general, resins and other materials requiring organic solvents have not been better than coating materials which are soluble in aqueous media, so that the art has substantially universally used coating materials soluble in water. By and large, the most commonly used coating materials for protecting glass fibers, during the forming operation comprise starch in some form. Although starch is not durable to the degree that it can stay in place on the filaments and provide protection after the fibers are woven, it has been without equal in its protection of the strands during the various abrasion producing operations that are involved preparatory to, and during, weaving. In addition, methods have been developed, usually burning, which are quite satisfactory for removing the starch after weaving, so that any desired finish coatings can then be applied. The art has long desired to replace starch base coatings, which are only temporary in nature, with a single coating material which would perform as satisfactorily as starch base materials during forming, and which would act as a finsh size which is capable of being dyed and which will permanently protect the filaments during use. The art would further like this coating material to be a universal one, so that it can be used regardless of the end use of the strand. Such a universal coating material for glass fibers has never been developed, and there is considerable belief in the art that one will never be developed, because of the great number of properties which such a material must have.

Coating materials, including starch base coating materials, must be quite fluid when applied to the filaments, in order that the coating materials will completely cover, or wet out the filaments in the short length of time that exists before they are brought together into a strand. The amount of solids that can be applied to the filaments, therefore, is limited by the degree of fluidity necessary to wet out the filaments. It is not possible to apply fluid coating materials in an amount which will completely wet out the strands without having an excess present, and a high percentage of the coating fluids brought in contact with the filaments is thrown into he surrounding area as a spray. In addition, the coating collects at ditferent areas of the applicator and Winding equipment which then either drips or is thrown to the floor. In all prior art processes with which applicants are aware, the degree of fluidity required necessitates that the coating fluids have only a small percentage of solids, and a high percentage of the coating materials that are carried with the strand into the coiled package is the solvent. The coiled packages of strand which are produced must be dried prior to subsequent twisting and weaving operations, and during this drying operation, the movement of the fluid or solvent migrates to the surface of the package and carries along with it some of the solid materials which form the coating. This movement of the solid materials with the solvent is commonly called migration. The art has long been concerned with the problem of migration and a considerable number of patents have been concerned solely with this single problem.

According to the concept of the present invention, a new and improved method of applying coating materials to fibers, and particularly glass fibers at forming, is provided which will allow the various already developed coating materials to be applied to the fibers in a manner which overcomes some of the problems which the prior art has tried to overcome by specially developed coating materials.

Accordingly, it is an object of the present invention to provide a new and improved method of applying coating materials to glass fibers at forming which substantially eliminates the spray and other types of loss of the coating material to the surrounding area.

Another object of the invention is the provision of a new and improved method of applying coatings to fibers which will allow a greater concentration of solids to be applied to the fibers.

Another object of the invention is the provision of a new and improved method of applying coatings to glass fibers at forming which substantially completely overcomes the problem of migration.

A further object of the invention is the provision of a new and improved method of coating glass fibers, and particularly glass fibers at forming, wherein the coating material is either a reversible shear thinning gel, or is contained within a reversible shear thinning gel, and the coating material is caused to flow around the fibers as a liquid and then revert to a gel.

Further objects and advantages of the invention will become apparent to those skilled in the art to which it relates from the following description of the method of the present invention, as well as numerous examples of materials which can be applied to the fibers according to the method of the invention.

SUMMARY OF THE INVENTION According to the invention, a reversible shear thinning gel producing agent is incorporated in the lubricating or film forming solutions that are applied to fibers, and particularly glass fibers, to produce a coating which forms a reversible shear thinning gel under predetermined conditions. The shear thinning coating materials can be applied to the fibers either from a gel or from a solution, and the coated fibers subjected to the predetermined conditions which causes the coating to revert to the gelatinous state. The fibers coated with the solutions can be brought into touching engagement and then converted into the gelatinous state, or the coatings can be converted into a gel prior to the time that they are brought into touching engagement with other fibers. It has been found that even though the fibers are embedded in a shear thinning gel in the package, they can be removed from the package without being ripped free of the gel. The shearing action of the fiber through the gel causes the gel to revert to a fluid which adheres to the fibers and reforms into a gel when the fibers are clear of the package. In addition, the gelatinous state reduces migration of the film forming materials and other constituents during evaporation of the solvent forming the coating solution.

Another advantage of the present invention is achieved by causing the coating solutions to be transformed into a gel around the fibers prior to being brought together into the package. The gelatinous state helps to hold the material onto the fiber to prevent the materials from being thrown from the fibers even though the fibers travel at very high speeds. In addition, greater amounts of the coating materials can be caused to adhere to the fibers. It is not necessary in all instances to convert all of the coating solution into the form of a gel since a definite advantage is achieved when only a surface of the coating solution is transformed into a gel. This skin of gel forms a type of shell which accomplishes some of the same advantages that are achieved when all of the solution is transformed into a gel. A skin of gel can be obtained by the evaporation of solvent to increase the concentration of solids in the surface layer of the coating to a degree where the surface layer is transformed into a gel.

In still other instances, the principles of the present invention can be achieved by applying the coating solutions to the fibers under thermal conditions in which the material is a liquid, and by thereafter subjecting the coated fibers to thermal conditions which causes the solution to revert to a shear thinning gel. In one convenient method of operation, the coating solutions can be applied to the fibers hot, and after the hot solution surrounds the fibers, the coated fibers are subjected to a temperature below the gelation point to cause the coating to revert to a gel. This method of operation has the big advantage in that coating solutions of high solid content can be caused to flow around the fibers to coat the fibers, following which the material is locked onto the fibers by the reversion of the material to the gelatinous state. It is therefore possible to produce coatings of sufficient solids content to fill the voids between packed fibers without the further impregnation of the packed fibers by additional solids. This has particular advantages where the coatings are resinous in that fiber reinforced resins can be produced without a later impregnation step.

The fibers can also be coated by drawing the uncoated fibers through a body of reversible shear thinning gel to subject the gel to shear and thereby cause the gel to revert to a liquid which flows around the fibers. The liqud coating then reverts back to a gel when the fibers have moved clear of the body of gel. By causing the coating materials to revert to a gel immediately after coating, spray or throw off of the coating material from the fibers is substantially eliminated, and the contamination of the surrounding area with the coating materials is substantially eliminated. The advantages of having the coating materials present on fibers in the form of a shear thinning gel are numerous, and various other advantages and modifications for techniques for producing the same, will occur to those skilled in the art to which the invention relates.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph of viscosity versus shear rate of one embodiment of coating material which has a pronounced point of transition from the gelatinous state to the liquidous state;

FIG. 2 is a graph similar to FIG. 1 showing another shear thinning coating material wherein the transition state is more gradual;

FIG. 3 is another graph similar to FIG. 1, but showing the thixotropic nature of a thin solution;

FIG. 4 is a graph of the same type of solution as used for FIG. 3 excepting that it is of a high solids content;

FIG. 5 is a graph similar to FIG. 1 showing the change in viscosity of a coating material having high solid content when at a temperature above the gelatinous point; and

FIG. 6 is a graph similar to FIG. 5, but showing viscosity change at a temperature below the temperature of gelation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In one form of the invention, the filaments or fibers are drawn over a reversible shear thinning material which is broken down into a solution to flow around the fibers by reason of the shear produced as the fibers are drawn through the material, and which solution thereafter reverts to a thickened or gelatinous state immediately after being removed from the shear producing forces. According to the invention, it has been found that fibers drawn over a surface coated with a reversible shear thinning gel will produce a shearing action in the film of gel which will cause the fibers to be completely and uniformly coated with the material. The degree of uniformity of the coating so produced is unexpected since fibers cannot be drawn over conventional gels to coat the fibers. Conventional gels resist transfer from the body of gel to the fibers, and generally do not adhere to the back side of the fibers. That portion of conventional gels which is picked up by fibers drawn thereover is retained on the fibers more by mechanical action than by adhesion. It has been discovered that reversible shear thinning gels do more than coat the surface that is brought to bear upon the gel, in that the shear thinning materials flow to the back side of the fibers where they adhere equally well. The coatings produced by drawing the fibers over shear thinning gels are satisfactory and uniform, at least to a degree where the fibers coated therewith will prevent glass to glass abrasion throughout all forming, twisting, and weaving operations which glass fibers are subjected to.

Numerous materials are known to produce reversible shear thinning gels. It has been found that substantially any of these materials can be used to make a gel of any of the previously used coating materials for fibers. Not only are fibers drawn over these gels adequately coated, but substantially none of the gel is lost in the process. The coating operation using reversible shear thinning gels, therefore, is extremely efficient, and makes possible the economic use of materials which were formerly thought to be too costly for use as a coating on glass fibers. It has also been found that shear thinning gels containing a considerably higher percent of solids than the prior art coating solutions, emulsions, or suspensions, can be satisfactorily applied to the fibers. The process of the present invention wherein the fibers are drawn over reversible shear thinning materials to transfer material from the applicator to the surface of the fiber has so many advantages that it well may make all prior methods of applying materials to glass fibers at forming obsolete. The possibility that reversible shear thinning gels could be used to uniformly coat the fibers could not be foreseen, nor could the many advantages of the method of the present invention be predicted.

A considerable number of materials, both organic and inorganic, are known to produce reversible shear thinning gels, and these materials are broadly called thixotropes. The precise structure of gels generally, and shear thinning gels in particular, has not been clearly established, but it is postulated that they form a network by means of secondary bonds which will surround and enclose other materials including solvents. In some instances the solvents, if they are polar, will join in the network by means of Van der Waal bonds to cross link from one particle of gel former to another. In other cases, it is believed that the particles of the gel former align through secondary forces to form the network. In a shear thinning gel, shear forces disrupt the secondary bonds to break down the structure and cause it to behave in a manner similar to a solution. As soon as the shear forces are removed, however, the materials align themselves into a network again which encloses the solvent and causes the composition to assume a gelatinous state. As previously indicated, shear thinning gels can be made in both aqueous and organic solvent media to produce shear thinning gels of slightly different structures. All types of shear thinning gels regardless of the media, can be used to adequately coat fibers, and particularly glass fibers at forming. Since all types of reversible shear thinning gel producing materials are by dictionary definition called thixotropes, and since all known thixotropes have been found to produce gels suitable for coating glass fibers at forming, these materials have been referred to in the parent specification and claims as thixotropes or thixotropic agents. Recent technical literature, however, seems to limit use of the word thixotropic to refer to systems which exhibit a sudden drop in viscosity--accompanied by a breaking of the gel structure. The word pseudoplastic has been used to refer to a gradual changing or thinning of the gel structure to the viscosity characteristic of a liquid. Both pseudoplastic and thixotropic materials fall within the broad dictionary definition of thixotropic as used heretofore. Similarly, the word gel is used in a broad sense to connote the gel forming mechanism rather than the provision of any specific degree of rigidity.

The following is an example of an organic thixotrope which makes a suitable thixotropic gel with an organic solvent suitable for application to glass fibers at forming.

Example 1 Parts by weight Diacetone alcohol 170 Polyvinyl acetate 20 Thixcin R 1 10 Thixcin R is a trade name of an organic thixotrope sold by the Baker Castor Oil Company, it is a high melting (ca. C.) ester of castor oil.

This material was prepared by mixing the polyvinyl acetate in a hundred parts of diacetone alcohol until the polyvinyl acetate was solubilized, following which the remainder of the diacetone alcohol was added. This material was put in a Waring blender, and the Thixcin R added with the Waring blender run at a high speed, and with the temperature of the material at approximately F. A very good thixotropic gel is produced which can be pumped to a rounded surface over which glass fibers are pulled as at forming. The fibers so coated emerge with a film of thixotropic gel completely coating the fibers which upon evaporation of the solvent, leaves a film of the polyvinyl acetate completely coating the fibers.

The following example illustrates that resins and other materials can be incorporated with the thixotrope to produce a gel of the resins.

Epoxy 1 has the following formula:

OHa

wherein n=0.

Epoxy 2 has the same formula excepting 11:3.

This material was prepared by mixing the epoxide polymer with the diacetone alcohol in a Waring blender to form a solution, and thereafter adding the Thixcin R. The blender was run at high speed for five minutes, at a temperature of approximately 112 F., and the material prepared was a good thixotropic gel which completely surrounds glass fibers when pulled therethrough. Upon evaporation of the solvent, an epoxide resinous coating remains on the fibers.

The following examples illustrate that substantially any resinous material can be made into a thixotropic gel. These materials were prepared in generally the same manner described above, and they all uniformly coat glass fibers to leave a generally uniform film of the resin which completely surrounds and coats the fibers.

Example 3 Parts by weight 15 Butyl Cellosolve stearate 1'90 Thixcin R 10 Example 4 Water soluble epoxy resin 1 50 20 Diacetone alcohol 142 Thixcin R 8 1 See the following formula:

8 Example 10 Parts by weight Diacetone alcohol 76 Monazoline 1 (1 hydroxyethyl, 2 alkylimidazoline wherein the alkyl radical is a C unsaturated chain) 4 Refined attapulgite (3MgO-1.5Al O -8SiO -9H O) 2O H PO 0.5

1 The Monazoline has the following formula The gel was prepared by dissolving the Monazoline in the diacetone alcohol and then adding the thixotrope. The material was mixed in a Waring blender for five minutes. Thereafter, the phosphoric acid was added and thoroughly mixed to produce the thixotropic gel. This material uniformly coats glass fibers drawn therethrough.

The next example illustrates that resins and other materials can be incorporated into a thixotropic gel using the same thixotrope.

l O N(ROH')2 (5:0 I i 11.

Example 5 Example 11 Octodecylamine 15 Parts by weight Isopropanol 100 Epoxide resin (1) 7.6 Thixcin R 12 Epoxide resin (2) (70% solids) 3.3 5% Aqueous polyvinyl alcohol solution 100 Gamma amino propyl triethoxy silane 0.3 Example 6 Diacetone alcohol 64.2

Parts by weight Archer Daniels aerofiint 303X90 (Oxirane modi- Parts by weight Acrylic resin (Rohm & Haas acryloicl A10 30% solids) 10 Thixcin R 4 Cellosolve acetate 86 Example 9 Parts by weight Epoxide (1) 30 Gamma amino propyl triethoxy silane 1 Butyl Cellosolve stearate 80.5 F Diacetone alcohol 80.5 Thixcin R 8 The following is an example of another organic thixotrope which forms thixotropic gels in organic media suitable for application to glass fibers.

Monazoline Refined attapulgite (3MgO-1.5Al O -8SiO -9H O) 20 H PO 0.4

This material was prepared in the same manner given above, and likewise uniformly coats glass fibers, to in this case leave a uniform coating comprising the epoxide and other ingredients.

The following is an example of an inorganic material which forms a thixotropic gel in an aqueous media. This gel likewise uniformly coats glass fibers when drawn therethrough.

Example 12 Parts by weight Baymal alumina 2.8 NH OH 0.5 Water 70 Example 13 Parts by weight Polyvinyl alcohol 24 Water 800 H O soluble copolymer of methyl vinyl ether and maleic anhydride 8.5

The thixotropic gel was prepared by mixing the PVA in water at room temperature, following which the copolymer of methyl vinyl ether and maleic anhydride is added and vigorously mixed for five minutes. This material is a thixotropic gel and forms a uniform coating on fibers drawn therethrough.

The following is an example of another organic material which forms thixotropic gels in aqueous media.

Example 14 Parts by weight Polymer of ethylene oxide (MW 1,000,000+) l Condensate tetraethylenepentamine and stearic acid 0.2 Kelzan (polysaccharide gum) 1.0 Union Carbide L-77 (Nonionic organosilicone surfactant) 0.01 Water h 88.79

Made by Kelco Company. A polysaccharide gum produced gy fterrnentation of an alginate with Xanthomonas comphestm's ac enum.

Example 15 Parts by weight Cationic corn starch (CATO 75) 175 Carbopol (thixotropic agent manufactured by B. F.

Goodrich Chemical Co. as per Patent 2,798,- 053) 10.5 NH OH (28%) 7.9 L-77 0.35

Water 3500 Example 16 Parts by weight Water dispersible bentonite clay (Bena qua) 1 10 Micro-crystalline cellulose (Avicel-C) Water 485 1 A highly beneficiated hydrous magnesium montmorillonite having an average chemical analysis of about 53.7 percent SiOs, about 24.5 pezcent MgO, and about 12 percent loss on ignition.

This material was prepared by preblending the Benaqua and Avicel-C powders and then adding this blend to water in a heavy thixotropic gel which will carry other materials, such as starches, etc. with it when applied to glass fibers in the manner given above. Gelling materials can be easily applied to the fibers by the applicators disclosed in application Ser. No. 573,348 filed Aug. 18, 1966.

The following example is exemplary of dye containing materials which can be made and applied to fibers without contamination of surrounding fiber making operations, and which will not discolor other fibers with which the dye containing fibers are mixed. These materials can be used as tracer yarn in gun roving for visual indication of fiber distribution in hand lay-up operations.

Example 17 Desirable Preferred wt. range, weight, Material percent percent Film former 1-30 Polyvinyl acetate- Gelling agent Carbopol 934 (polycarboxy Pontamine fast red Cathionio lubricant- AHCO 185 AE-.- AHCO 185 AN-.. N0l1l8l'li(tl)1l1brl0a{lg60 .(.i H-f 1"... ar owax po yet ene ycol ester MW. 1,000) y g Coupling agent Gamma amino propyl triethoxy an Aqua ammonia (28%) pH controL Vehicle Balance 1 Pontamine fast red has the formula:

l SOaNu The above composition is made by making a water dispersion of the dye, a water solution of the thixotropic gelling agent, and a water solution of the cationic and nonionic lubricants, and then adding the dye and gelling agent premixes to the dispersion of the cationic and nonionic lubricants. Thirty-five parts of deionized water is added to a mixing kettle followed by the addition of 16.6 parts of the pontamine fast red dye. One part of aqueous ammonia is added and the materials mixed until a smooth dispersion is obtained. In another mixer, 92.9 parts of deionized water and 3.12 parts of the carbopol 934 is added and mixed until homogeneous. Thereafter 0.20 part of ammonia are added to the gelling agent premix and the dye premix is blended in. In another mixer, 20 parts of deionized water, 0.52 part of AHCO 185 AB and 2.24 parts of AHCO 185 AN are added and stirred into a solution at F. Thereafter 0.30 part of ammonia are added to give a smoothdispersion, and it is added to the gel-dye mixture. Thereafter 29.1 parts of polyvinyl acetate is added slowly and completely dissolved, and 0.80 part of ammonia are added and mixed until a smooth gel is obtained. Thereafter additional ammonia is added to bring the pH to between 6 and 6.5. The material is then applied to glass fi'bers at forming as above described to give a red colored strand which can be twisted with other strand Without dye transfer and which can be used in a gun chopping and spraying operation for glass fiber reinforced polyester resin lay-ups, etc. as a tracer yarn for indicating fiber distribution.

Example 18 The following is a gel forming material containing a polyester resin:

lVlethacryloxypropyltrimethoxysilan Lubncant .e 0-10 PE G 400 (Polyoxyethylenemonoleate) 0. 35 Emulsifying agent 020 ulfonated mineral oil 0. 25 Deionized water Balance 87. 89

Example 19 Materials: Percent by weight Selectron 5930 2.50 Avicel C 4 Methacryloxypropyltrimethoxysilane 0.79 Sulfonated mineral oil 0.25

Water Balance Examples 18 and 19 are prepared in substantially the same manner as is the material of Example 17.

The material of Example 19 when applied to glass fibers by the applicator disclosed in application Ser. No. 573,348 provides approximately 1% of solids on the coated fibers. After the fibers are coated With the size, they are drawn together into a strand, which in the present instance comprises 408 fibers, and the strand is coiled into a package, and the package dried. A plurality of these strands is then dipped into an organic solution of the same Selectron 5930 polyester resin having approximately 50% solids. The resin coated strands are then pulled through a die which removes excess resin and shapes the impregnated strands into the form of a rod. The resin forming the rods is then cured, and in the case of Example 19, the rods contain approximately 50% by weight of resin solids. Fifty percent retention of resin in an impregnating process is unusually high, and is believed to occur by reason of the particulate nature of the microcrystaliine cellulose (Avicel C) gelling agent which is used in Example 19.

Shear thinning gels can be produced by two types of gelling action or phenomena. One type of gel structure occurs when the molecules of a gelling agent arrange themselves in long, linear chains which hold solvent on the exterior surface of the chains by secondary forces, such as Van der Waal forces, etc. This type of gelling agent produces gels which have been characterized as pseudoplastic, and which gradually change from a condition having the rigidity of a gel into a material having the fluidity of a solution.

Another type of gel structure is produced by a type of gelling agent which forms a cage type structure which holds the solvent internally of the cage. These cage structures attach themselves weakly to other cage structures by means of secondary types of bonds to form gels. When this type of gel is subjected to increasing amounts of shear, a point is reached Where the cages are moved past each other fast enough to prevent regrouping, and a sudden drop in viscosity is noted. This sudden drop is sometimes referred to as a breaking of the gel, and as pointed out above, the Word thixotropic has recently been more narrowly defined to be specific to this type of gelling mechanism. Thixotropic gelling agents, therefore, in the narrow sense, produce cages or particles which tend to separate the fibers of a strand so that the strand has greater space between the fibers and is capable of holding a greater amount of impregnating material than is the case when pseudoplastic gelling materials are used. Examples of particulate or thixotropic gel producing agents are Baymal, water dispersible 'bentonite clay (Benaqua), Thixcin R, guar gum and polyacrylamides. These materials, therefore, will have particular advantages when used as a gelling agent in the broad formulations given in Example 18.

Another specific example is as follows:

Example 20 Materials: Percent by weight Selectron 5930 2.5 Methocel (50,000 cps.) 0.5 Methacryloxypropyltrimethoxysilane 0.5 Sulfonated mineral oil 0.5 Acetic acid 0.3

Water Balance 12 Example 21 Gels of rubber producing Latex, either natural or synthetic, can also be made and applied to fibers. Suitable materials can be produced as follows:

Desirable Preferred wt. range, weight, Material percent percent;

Elastom eric latex (solids) 5-50 Butadiene-styrene latex solids) 15 Resorcinol formaldehyde latex (40% solids) 10 Coupling agent 0. 1-10 Gamma aminopropyltrimethoxysilanc 2 Gelling agent 0. 2-15 Avicel O 6. 0 Methocel Solvent B alanee Water a Balance 1 Methocel is a cellulose gum of these types:

(1) Methyleellulose. (2) HydroxyproDYlmethylcellulose. (3) Hydroxybutylrnethylcellulose.

The gels of the latex are made by dispersing the Avicel in water followed by the addition and dispersion of the methocel. The mixture is then run through an homogenizer to produce a very high bodied gel. The latex is then added with stirring and is thoroughly incorporated. The material when applied to glass fibers at forming using the gel type applicator above described gives a uniform coating of approximately 9 percent solids.

Example 22 A nylon coating material which produces a gel is made as follows:

Emulsifying agent Sulfonated mineral 0 Solvent Water The nylon coating material was prepared by the following procedure. The nylon is dissolved in a suitable solvent, such as tetraethanolamine, phenol, or a lower alcohol such as methanol, or ethanol. The emulsifying agent is added slowly to /1 of the water and the nylon solution is then added with violent mixing to form an emulsion. Upon standing, some of the solvent evaporates from the particles of nylon so that they solidify and form a dispersion. In another Eppenbach mixer, the gelling agent is added to one fourth of the water until completely dissolved, and the tetraethanolamine is added. The nylon dispersion is then added to the gelling solution, and the mixer is run at maximum speed until a thick White creamy gel is formed. The coupling agent is then added, and the material is applied to glass fibers at forming as above described.

The 3-(trimethoxysilyl)propyl methacrylate given in the example above is used to provide wash fastness for fabric produced from the coated fibers. It will be understood that -a high degree of coupling is not desired in some types of textiles, and that, therefore, a coupling agent is not necessary in all instances. Cationic lubricants are used for providing lubrication for fibers when drawn over numerous guide surfaces in a wetted condition. A cationic lubricant, therefore, is also not necessary in all instances. Similarly solvent for the nylon will not be necessary if the nylon is of low molecular weight.

13 Example 23 Another nylon coating material was formed as follows:

The nylon 66 was dissolved in five times its weight of isopropanol at 100 F. The dissolved nylon was added to the Cellosolve acetate at 100 F., and the gamma aminopropyltriethoxysilane was thereafter thoroughly mixed therewith in an Eppenbach mixture. After the materials were thoroughly blended together, the Thixcin R was added, with the mixer running at full speed and with the The polytetrafiuoroethylene used is an emulsion polymerized material stabilized with sulfonated mineral oil and containing 60 percent solids and 40 percent water. The Aqua ammonia was mixed with this dispersion with a spatula. The Carbopol 934 was added to the water in an Eppenbach mixer, and the coupling agent added thereto with continued stirring for 10 minutes. The emulsifying agent was then added and stirred until it was incorporated into the solution. Thereafter, the solution of ammonia and fluorohydrocarbon was added slowly into the mixture with extreme agitation until a smooth clear gel forming material was produced. This material is applied to glass fibers at forming as above described and gives a uniform protective coating.

Example 26 The following is an example of a gel size for coating glass fibers to be used in producing bonded staple.

materials heated to a temperature of 118 F., to form a g g g gel. This material was applied to glass fibers at forming Material w bg f g w 5 to ive a uniform coatin on the fibers.

g g Oxirane modified polyester solids 3-20 Adduct of polyester and epichlorhydrin Example 24 (90%Solids, xylol) 13 Polyester resinsolids A gelling rubber stock is made as follows: Qgggg methyhsobutu 13 Lubricant 0-10 White mineral oil 3. 39 Gelling agent 0. 2-15 Desirable Preferred Thix in R 3 wt. range, weigh Solvent Balance Material percent percent (lellosolve acetate 67. 61

Rubber stock 10-50 Styrene butarliene Solvent 50-90 Toluene 80 Gelling agent 0. 2-15 Carbopol 934 3 The gel forming material is made by chopping the rubber stock sheet into small pieces approximately 4 inch square and adding them to /2 of the solvent with constant mixing. The gelling agent is dissolved in the other half of the solvent and the rubber solution then mixed therewith. This material is a pseuoplastic gel at room temperature. When the material is applied to glass fibers, as above described, it uniformly coats the fibers and gives an ignition loss of approximately 9.3 percent.

Example The following is an example of a tetrafluorohydrocarbon gel forming material which can be applied to the glass fibers:

Desirable Preferred range, weight, Material percent percent Gelling agents 2-15 Carbopol 934 r 0. Polytetrafiuorohydrocarbon- 1-20 Polytetrafluoroethylene 3 Coupling agent 0-3 Gamma methacryloxypropyltrimethoxysilane 0. 50 Emulsifying agent 05-5 Sulfonated mineral oil- 0. 36 Aqua ammonia adjust pH 7 to 8.- Solvent for the fiuorohydrocarbon 5-20 Tetratluoroethylene monomer 2 Water 1 Balance.

H HMatoll-..io o oi clo w The following is an example of a size for glass fibers to be used as a thermal plastic or thermosetting resin reinforcement.

Desirable Preferred wt. range, weight,

Material percent percent Nonhardening phenol-epichlorhydrin adduct solubilized with an alkauol amine and end Stopped with a polyglycol 0 5-10 Bisphenol A-epichlorh ydrin adduct end stopped with polyethylene oxide monooleate M.W. 400 and diethanolamine in Organo-silane coupling agent A dGamma aminopropyltriethoxysilane.

' a Meth cel (50,000 cps.) Deionized water *The adduct has the following formula:

o-OlIl where R1 is an ethyl group, 0R is a monooleate radical c2400 M.W.

Example 28 The following is another example of a gel size for application to glass fibers to be used in reinforcing a thermal plastic or thermosetting resin.

Desirable Preferred wt. range, weight Material percent percent Nonhardening end stopped phenolepichlorhydrin adduct solubilized with an alkano- 1 lamina and an acid -10 BisphenolA-epichlorhydrin adduct end stopped with polyethylene oxide monooleate M.W. 400 and diethanolamine in 1:1 ratio 1. 0 Saturated polyester resin 0. 1-5

(1 mol phthalic anhydride, 1 mol sucr cinic anhydride, 2.3 mols propylene glycol cooked to an acid number of 35- 0 5 Alkanolamine adduct of phenol-epichlorhydrin epoxy prepolymer 0. 1-3

Bisphenol-epichlorhydrin dduct solubilized by diethanolamine and acid 1 0. 3 Organosilane coupling agents 0 1-10 2O Ga%ma aminopropyltrictho Acid Acetic acid- Emulsifying agent Polyethylene glycol Stcaric acid adduct (400 molecular weight) 2 Gclling agent 0. 2-15 Methoc 0. 5 pH Adjustment- 2 3. 8-5. 8 H 2 4. 8 Balance Balance 1 The adduct has the following formula:

Example 29 The following is an example of a thixotropic coating for application to glass fibers for use as a weavers roving:

Desirable Preferred wt. range, Weight, Material percent percent Nonhardening phenol-epichlorohydrin adduct solubilized with an alkanol amine and end stopped with a polyglycol 0. 5-10 Bisphenol A-epichlorhydrin adduct end stopped with polyethylene oxide mono- M W 400 and diethanolamine in 1 0. l-3 Bisphenol-epichlorh o1 bilized by diethanolamine and acid 1 c. 0.3 Organo-silane coupling agent- 0 3-3 Garmna methacryloxyprop oxysilane 0. 5 Acid r 0. 3

ari (400 molecular weight) 2 Gelling agent 0. 2-15 Methocel- 50 Water Balance Balance 1 This material has the formula: Same as above except 0R2 is a monostcarate radical.

Example 30 The following is a size for glass fibers to be used for reinforcing epoxy resin:

Dtesirable Prefeniietd w range werg Material percent percent 16 Example 31 The following is an example of an acrylic gel size for staple:

Desirable Preferred wt. range, weight Material percent percent Acrylic polymer 2-20 Acrylic polymer 7 Cationic lubricant 0-10 Condensate of tetraethylenepentamine and stearic acid 0. 28 Gelling agent 0. 2-15 Thixcin R 4. 0 Solvent Balance Cellusolve acetate Balance Example 32 The following is an example of an epoxy resin gel size for coating fibers used to reinforce epoxy resins:

The following is an example of the formulation of an epoxy resin dispersible in an aqueous gel.

Example 33 Desirable Preferred wt, range, wt range, Material percent percent Epoxy resin 1-40 Dow Chemical DER 2. 72

Solvent for the epoxy resin Diacetone alcohol Emulsifying agent t Methocel 50,000 cps. Methocel 15 cps. Coupling agent Gamma glycidoxy propyltrimethoxysilane Acid.

Acetic acid ater B alance Balance Example 34 The following is an example of a gel size of an organosilane coupling agent generally devoid of a film former. The composition forms a thin coating over which a polymer can later be applied as occurs during filament winding of tanks, pipes and pressure vessels.

Desirable Preferred wt. range, wt., Materials percent percent Gelling Agent 0. 2-2. 0

Crosslinked polyacrylamide (Gelgard M of Dow Chemical Co 0. 3 Organosilane Coupling Agent- 0. 1-2. 0 Gamma amino propyl triethoxysilane 0. 7 Siloxane coupling agent and Lubricant 0-2. 0 Dirnethyl polysiloxane 0. 15 Siloxane terpolymer of a trirncthyl silane, methyl phenyl silane and a methyl ethylene oxide silane 0. 15 Emulsifying Agent 0-2. 5 Isooctyl phenyl ethoxy ethanol. 0. 15 Balance Balance In the above example, the emulsifying agent is used to disperse the siloxane lubricant,

1 7 It will be seen that useful gelling sizes for coating glass fibers can be made from any film former in generally the following proportions:

For coating materials which are to be tightly bonded to the glass fibers, at least 0.01 percent of a glass coupling agent such as an organosilane is needed. Where the coated fibers are to be run through textile forming machinery, at least 0.1 percent of a nonionic lubricant is needed. Where the fibers are flexed against each other in a wetted condition to any extent at least 0.01 percent of a cationic lubricant is also necessary.

Carbopol, Methocel and cross linked polyacrylamide may be considered as pseudoplastic gelling agents. As previously indicated pseudoplastic gelling agents produce gels which do not have a sudden break in viscosity during the transition from the gelatinous state to the solution state. The pseudoplastic gelling agents are believed to link up into long chains or lattices whose external surfaces hold the solvent by means ofsecondary bonds or forces.

Thixcin R, microcrystalline cellulose, Benqua and Baymal are examples of true thixotropic gelling agents which, as previously indicated, produce gels Which have a sharp reduction in viscosity at the breaking of the gel during transition from the gelatinous state to the solution state. In all the examples given above, the preferred compositions were either nonflowable gels through which the fibers are drawn, or are thin fiowable gels through which the fibers are drawn. The fiowable gels exhibit the reversible shear thinning properties necessary for the practice of the invention, but do not have sufficient gelling agent to hold all of the solvent in a nonflowable, or rigid state. In those examples given above, wherein the solvent is water, and the gelling agent is Methocel in a concentration below approximately 2 percent, the gel formed is a reversible shear thinning fiowable gel that is pourable, and which sets up into a firm gel in the package during the evaporation of water. The examples given above wherein the solvent is water and the gelling agents is Carbopol, in a concentration of approximately 0.2 percent, are also fiowable gels which set up more firmly in the package upon the evaporation of water. When Carbopol is used in water at a concentration of approximately /2 percent and the mixture is neutralized with a base such as ammonia, the material sets up into a rigid pseudoplastic gel. This same result is achieved using 5 percent Carbopol in water without neutralization.

In the examples given above contammg an organic solvent, and Carbopol in a concentration of approximately less than 0.5 percent, flowable nonrigid gels are produced. In those instances where the solvent is a volatile solvent such as toluene etc., evaporation takes place at the surface to form a skin of thickened gel. This skin thickening action starts to take place a short distance away from the applicator before reaching the package.

In an organic system using Carbopol, and a low concentration of for example approximately 0.5 percent, it is possible to subject glass fibers coated therewith to the neutralizing action of ammonia to form a r1g1d gel prior to being wound into the package.

In those examples using Thixcin R as a gellmg agent, it is also possible to apply the composition to the fibers at a temperature of above approximately 120 F. wherein the compositions are liquid and immediately thereafter cool the fibers to convert the coating to a gel prior to being wound into the package.

It would be understood, however, that the preferred procedure is to draw the fibers through a material that is a nonflowable gel, either of the pseudoplastic or of the thixotropic type, in order that the fullest advantages of the shear thinning gelatinous state is obtained. This gives the largest concentration of solids on the fibers, the minimum loss of material to the surrounding area, the minimum migration, and the greatest transfer efliciency. The use of the truly thixotropic gelling agents are the most preferred materials, because of the sharp drop in viscosity which gels made therefrom exhibit, and because the sharp drop in viscosity facilitates the flow of the material around the fibers during application.

While the invention has been described in considerable detail, we do not wish to be limited to the specific embodiments described, and it is our intention to cover hereby all novel adaptations, modifications, and arrangements' thereof which will occur to those skilled in the art to which the invention relates.

We claim:

1. A method of coating glass fibers comprising: solubilizing coating materials including a reversible shear thinning gel forming agent to produce a composition having reversible shear thinning gel properties under predetermined conditions, delivering said composition to an applicator, pulling fibers past said applicator and causing said coating material delivered to said applicator to fiow around and coat said fibers, and subjecting said coated fibers to said predetermined conditions to cause said shear thinning gel properties to develop in the coating materials on said fibers.

2. The method of claim 1 wherein the coated fibers are coiled in a package and the coating on said fibers are caused to develop said reversible shear thinning gel properties in said package.

3. The method of claim 1 wherein the coated fibers are gathered together into a package, and said coated fibers are subjected to said predetermined conditions prior to being brought together into said package.

4. The method of claim 1 wherein said coating composition develops reversible shear thinning gel properties below a predetermined temperature, said coating materials are applied to said fibers above said predetermined temperature, and said fibers are subjected to a temperature below said predetermined temperature after leaving said applicator.

5. The method of claim 4 wherein said coated fibers are coiled into a package and are cooled below said predetermined temperature before being gathered together into the package.

6. The method of claim 1 wherein said coating composition develops reversible shear thinning gel properties upon evaporation of a solvent to form at least a skin, and said predetermined conditions occur when said coated fibers are subjected to evaporation of the solvent after being coated by said applicator.

7. The method of claim 1 in which the solids of the coating materials comprise the following parts by weight:

Film former 1-50 Coupling agent 0-10.0 Reversible shear thinning gel forming agent 0.2-15 Lubricant 0-10 8. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Polyvinyl acetate 1-30 Gelling agent 0.2-15 Dye 0.5-20 Cationic lubricant 0.1-10 Nonionic lubricant 0.1-10 Coupling agent 0-5.0

19 9. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Polyester 1-40 Gelling agent 0.2-15 Coupling agent 0.05-10 Lubricant -10 Elastomer solids -50 Gelling agent 0.2-15 Coupling agent 0.1-

12. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Nylon 1-3 0 Gelling agent 0.2- Coupling agent 0.1-10

13. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Polytetrafiuorohydrocarbon 1-20 Gelling agent 0.2-15 Coupling agent 0.1-3

14. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

15. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Acrylic polymer 2-20 Lubricant 0-10 Gelling agent 02-15 16. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Oxirane modified polyester 3-20 Polyester resin 3-20 Lubricant 0-10 Gelling agent 02-15 17. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Nonhardening epoxy resin-polyglycol end stopped 0.5-10 Coupling agent 0.1-10 Gelling agent 02-15 18. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Nonhardening epoxy prepolymer 0.5-10 Alkanolamine adduct of phenol-epichlorhydrin epoxy prepolymer 0.1-3 Saturated polyester resin 0.1-5 Coupling agent 0.1-10 Gelling agent 0.2-15

19. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Phenol-epichlorhydrin adduct solubilized with an alkanolamine and end stopped with a polyglycol adduct 0.5-10 Solubilized epoxy resin 0.3-3 Organosilane coupling agent 0.3-3 Emulsifying agent 0.5-20 Gelling agent 02-15 20. The method of claim 1 wherein the coating materials comprise the following in approximate parts by weight:

Epoxy resin 1-40 Coupling agent 0.3-3 Polysiloxane 0.1-1 Gelling agent 0.2-15 Emulsifying agent 0.01-10 21. In the method of producing glass fibers wherein molten streams of glass are attenuated into advancing glass fibers that are individually surface coated at a high rate of speed and substantially immediately after coating collected into a package of coated fibers, the improvement comprising: applying a coating material containing a thixotropic agent to the fiber surfaces by passing the fibers through the coating material under conditions which creates shear in the coating material adjacent the fiber surfaces and flowing said coating material under the effect of shear substantially fully around the fibers to cover the surfaces thereof, and transforming the coating material containing the thixotropic agent to a gel on the fiber surfaces prior to coiling the fibers into the package.

22. In the method of producing glass fibers wherein molten streams of glass are simultaneously cooled and pulled at a high rate of speed to produce glass fibers which are then passed over an applicator which applies a coating of a lubricant to the fibers and are coiled into a package formed by wrapping the fibers around a revolving spindle, the improvement comprising: producing a lubricant for glass fibers and which is a thixotropic gel, delivering said thixotropic gel to the applicator, pulling the glass fibers over the gel on the applicator, causing the relative velocity between the fibers and gel on said applicator to produce sufficient shear on the surface of the gel to transform the surface of the gel into a liquid, maintaining said shearing contact until the surface of the fibers are substantially completely coated, and causing the coating on the fibers to revert to a gel.

23. In the method of producing glass fibers wherein molten streams of glass are simultaneously cooled and pulled at a high rate of speed to produce glass fibers, which are then passed over an applicator which applies a coating of a lubricant to the fibers and are coiled into a package formed by wrapping the fibers around a revolv ing spindle, the improvement comprising: adding a thixotropic gel producing agent to a solution of a lubricant Which otherwise immediately wets out and spreads over glass, delivering the lubricant containing the thixotropic agent to the applicator, causing the applicator to deliver the lubricant containing the thixotropic agent to the fibers and under conditions which causes the lubricant to flow around the glass fibers, and transforming the lubricant containing the thixotropic agent into a gel which completely surrounds and coats the fibers prior to being coiled into the package.

24. In the method of producing glass fibers wherein molten streams of glass are simultaneously cooled and pulled at a high rate of speed to produce glass fibers which are then passed over an applicator which applies a coating of a lubricant to the fibers and are coiled into a package formed by wrapping the fibers around a revolving spindle, the improvement comprising: solubilizing a thixotropic gelling agent with a solvent therefor, intimately mixing a nongelling lubricant for glass fibers with the solubilized gelling agent, delivering the intimate mixture to the applicator, causing the mixture on the applicator to be in a gel thickened state, pulling the fibers over the gel thickened mixture on the applicator, causing the relative velocity between the fibers and the mixture on the applicator to produce sufiicient shear to cause the mixture to flow around and substantially completely coat the fibers, and causing the coating to revert to the gel thickened state.

25. The process of claim 24 where said solvent is a mutual solvent of said thixotropic gel forming material and said nongelling material.

26. The process of claim 25 wherein said nongellable material is in the form of an emulsion, and the emulsion is dispersed throughout the thixotropic gel.

22 References Cited UNITED STATES PATENTS 2/ 1962 Pataky 117-38 8/ 1966 Ihde et a1 260-22 U.S. Cl. X.R. 

